The Ohio River Story - Part V (GM-27)
The Falls of the Ohio, like many topographic features along the Ohio
River, have their origin in glacial events. Sand and gravel deposited
during the latest period of partial valley filling date from the most
recent glacial advance, which reached almost to Cincinnati. The fill
covered many low hills within the valley. About 15,000 years ago the ice
retreated from the Ohio River basin, and the river, no longer loaded with
glacial debris, began to cut downward. At Clarksville its course then lay
across a small knob of fossiliferous limestone. Here the falls were formed
as the stream cut downward. This is the only place along the Ohio River
where the riverbed is cut into bedrock from shore to shore.